A transmission for a vehicle and a transfer apparatus for a vehicle converts and distributes a rotative power speed input to an input shaft respectively and output the converted or distributed power from an output shaft. A gear mechanism, which is engageably controlled, is usually provided inside of the transmission or inside of the transfer apparatus. In order to prevent wear and overheating of a bearing and of the gear mechanism, lubricating oil is enclosed in a casing of the apparatus to be circulated, and thus each component is lubricated. Also, in order to prevent the lubricating oil from leaking out of the apparatus, oil sealing portions are formed between each rotational shaft and the casing. An oil seal, which mainly composes the oil sealing portion, may be called a seal lip. An annular member made of synthetic rubber, for example, is employed and retained by the casing. The annular member is slidably contacted throughout an entire circumference of the rotational shaft. The oil sealing portion does not necessarily support weight of the rotational shaft, however, it is common to lubricate the oil sealing portion by using the lubricating oil to restrain heat caused by friction and deposits of foreign substances such as sludge.
The applicants of the invention disclose examples of this kind of lubricating structures in JP H7-71612A and JP H8-200478A. The lubricating structure of the oil seal disclosed in JP H7-71612A is provided with an oil seal, bearings, an oil receiver guiding the lubricating oil into a clearance between the oil seal and the bearing, and guide ribs provided at a bottom wall of a mounting hole for the bearing. The oil receiver receives and accumulates the lubricating oil gathered by the gears located inside the apparatus, and the guide ribs guide the lubricating oil to the oil seal. An oil pump is provided in the lubricating structure in the gearing transmission disclosed in JP H8-200478A, and an input shaft serves as a driving shaft of the oil pump and a bearing retainer of a bearing, which supports the input shaft, serves as a housing of the oil pump. The oil pump pumps the lubricating oil, which is guided from an oil receiver, to a pilot bearing between the input shaft and an output shaft.
In the method disclosed in JP H7-71612A, the lubricating oil is accumulated by the oil receiver and is guided by utilizing gravity. Unfortunately, it is difficult to effectively lubricate the oil sealing portion with this method due to hindrance caused by a centrifugal force of the rotational shaft. That is, although the lubricating oil is needed most in the vicinity of a sliding contact portion between a surface of the rotational shaft and the oil seal, the lubricating oil tends to be scattered to an outer side by the centrifugal force. Also, in the method disclosed in JP H8-200478A, the lubricating oil is pumped by the oil pump. The method is preferable for metal portions such as bearings, however, there is concern that direct jetting influences the oil seal made of synthetic rubber. Namely, if the pressurized oil is constantly jetted to a certain portion of the oil seal, fatigue may occur in a part of the oil seal, leading to deformation, or durability decrease. Further, in the known structure, there are cases where all of the lubricating oil is flown out when the apparatus is not operated. In those cases, the lubricating effect is not achieved properly immediately after the start of the operation, and there is room for improvement.
The present invention has been made in view of the above circumstances, and provides a lubricating structure of a rotational shaft oil sealing portion which supplies a sufficient amount of lubricating oil in the vicinity of a sliding contact portion on a surface of the rotational shaft to effectively lubricate therearound and to achieve the proper lubricating effect immediately after the start of the operation without influencing the oil seal in a disadvantageous manner such as fatigue.